This relates generally to electronic devices, and more particularly, to electronic devices with displays.
Electronic devices often include displays. For example, cellular telephones, tablet computers, and laptop computers often include displays for presenting information to a user.
Liquid crystal displays contain a layer of liquid crystal material sandwiched between upper and lower polarizers. Pixels in a liquid crystal display contain thin-film transistors and electrodes for applying electric fields to the liquid crystal material. The strength of the electric field in a pixel controls the polarization state of the liquid crystal material and thereby adjusts the brightness of the pixel. A liquid crystal display may have an array of color filter elements to provide the display with the ability to display color images.
The pixels in the liquid crystal display can be illuminated using a backlight unit. The backlight unit may include a light guide layer. The light guide layer may be formed from a transparent material such as a transparent polymer. An array of light-emitting diodes may emit light into the edge of the light guide layer. The light that is emitted into the edge of the light guide layer may be distributed throughout the light guide layer in accordance with the principle of total internal reflection.
It may be desirable to use light-emitting diode light sources with spectrally narrow bandwidths to enhance the color gamut of a display. One way in which to produce spectrally narrow backlight is to use backlight light sources that are based on blue light-emitting diodes pumping red and green phosphors. This type of approach produces narrow-bandwidth blue, green, and red light, but may introduce undesired color shifts as the level of the backlight is adjusted. Temperature variations may also affect display color accuracy.
It would therefore be desirable to be able to provide improved ways for ensuring that color images are accurately presented on a display in an electronic device.